Winding for dynamo-electric machines



R. B. WILLIAMSON.

WINDING FOR DYNAMO ELECTRIC MACHINES.

APPLICATION FILED DEC. 1, 1916.

1,400,336, Patented Dec. 13,1921.

/2 12 w z 2 e 6 /2 2 V7 1 :1 Q' T 35 28 a2 2 m; 0 "a Z5 m /7 35% g 28 9 5 29 if 34 /7 17 I69 /6d UNITED STATES PATENT OFFICE.

ROBERT B. WILLIAMSON, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO ALLIS- CHALMERS MANUFACTURING COMPANY, OF MILWAUKEE, WISCONSIN, A

CORPORATION OF DELAWARE.

Specification of Letters Patent.

Patented Dec. 13,1921.

Application filed December 1, 1916. Serial No. 185,082.

To all whom it may concern-.-

Be it known that I, Rozannr lViLnnursoN,

acitizen-of the United S t-ates, residing at Milwaukee, in the county of'Milwaukee and- State of WVisconsin, have invented a certain new and useful Improvement in findings for Dynamo-ElectricMachines, o f'whic-h the following is a. specification;

This invention relates to an improved design of windings for dynamo-electric machines.

In the design and construction of certain types of dynamo-electric machines, especially alternating'current machines of comparatively large size, in order to reduce to a low value eddy currents which may be induced in a winding made up of a single conductor of comparativelylarge cross-sectional area, the tendency toward the production of such currents resulting from the difference in amount of magnetic flux surrounding different portions of the conductor, it may be desirable to split the conductor into a plurality of branches insulated from each other within the slots of the machine. Again,

where the conductor in the slot is fairly deep, that is, in a radial direction, different portions or strata of the conductor are atfected-to different extents by leakage flux, the portions of the conductor nearer the closed end of the slot consequently having greater reactance, the result being that cur rent may circulate through-the several parallel connected portions of the conductorand the effectivecurrent may be crowded to one portion o'f'the conductor so that that ortion of the conductor nearer the open en of the slot may carry more than its proper share of the totalcurrent.

lVith the conductor in the slots divided into' several insulated branches to avoid or materially reduce eddy current effects, un-' less these'branches are maintained separate throughout the entire winding or, at least, a section of theentire winding, and means are provided for equalizing the impedances of the branches, the effects of circulating currents and, generally, the unequal distribution of current in the several branches of the conductor may be such as to very noticeably aiiectthe heating and general efliciency of the machine. This will be apparent when it is considered that, with these branches maintained separate and insulated one from another throughout their length, there may exist the condition wherein one of the branches is carrying current considerably above a certain average value and another branch carrying current considerably below the same value, which value would, under ordinary circumstances, be that which either branch could carry without undue heating during the operation of the machine. This unequal division of the current in the several branches is wholly undesirable for it increases the heatlosses of the winding, these losses being a minimum when the current in the several branches is proportional to the ohmic resistances of the branches. In additionto this, it will be apparent that greatest economy in copper is realized .when all parts of the conductor are worked at the maximum safe current density.

In accordance with this invention, the conductor of'which the winding is constituted is divided into two or more branches in the slots of the core and means are provided for causing the current in the several branches to divide proportionally, thus, in addition to reducing eddy current losses to a low figure, avoiding losses due to circulating currents when these branches are connected together at their ends, and, generally, insuring that the conductors of the several branches are worked at the same current density.

The invention is carried out as to its general features by dividing the conductor into several parallel branches fully insulated one from another throughout the length of the conductor, and by adding an artificial reactance to that one of the several parallel circuits which may have the least reactance due to the position of portions thereof relative to the core, this addition of reactance being made preferably outside of the coreand in the end turns or, as it may be desirable, in the leads when the entire winding or one phase thereof is divided into several parallel branches disposed in the same slots and insulated from each other throughout.

It is an object of this invention to provide an improved winding construction for dynamo-electric machines.

It is a further objectto provide an improved winding for dynamo-electric machines wherein the conductor of which the winding is made up is divided into a phirality of parallel connected branches insusuch invention, and .will be particularly" pointed out in the claims.

In the accompanylng drawings: Figure l is a development of a portlon of a windingof the distributed type for use in ,7 the slots of the core of a dynamo-electric maportion or" one layer of the winding is dischine, and embodying features or" this invention.

Fig. 2 is a broken sectional view of a core showing portions of a winding ot the two layer type disposed in a slot of the core, each layer of the winding being made up of two parallel connected, insulated branches. 7 Fig. 8 is an end view showing the connections between the several branches of the winding of Fig. .1.

Fig. 4 is a broken end view of a core showing portions or" the winding of Fig. 1 in p ositioh in the slots of the core.

Figs. 5 and 6 are diagrammatic views illustrative of the general principle involved inthe invention. 1

in the drawings, the general invention is shown appliedto an ordinary form of windi or dynamo-electric machines. For purposes otillustration, this winding may be considered as a portion of a two-layer winding of the stationary armature of an alternating current generator. The stationary core 10 is provided with radial slots 7.2. i

posed in-the slots adjacent the air gap and a-portion of a second layer i l of the windisposed at the inner ends of the slots, being used to hold the winding ements in position; .The conductors torming the several layers of the windingare divided into a plui y of branches, the winding element i3. being divided into two brancheslfi and i7 insulated one from anfrom the layer of wind- --J3 l], mi th 0 pieierao y or p e same As illustrated generother and insulated ing 14, and being moss-sectional area.

.allv in Figs. 2, 3 ands, these several branches a tained insulated one from anilOllii several turns of the windany section of the winding, or even i a single Thesection oi the winding illus- Gr tl rou hout, the entire winding of phase.

trated maybe considered as a portion of a,

single phase winding.

Considering a slot-occupying portion of the conductor or winding element 13, it will be. apparent that the leakage flux bet-ween adjaeent teeth is dii-lerent for the several radially superposed branches 59, 51, the branch 51,. due to itsbeing effectively more remote as a whole from the air-gap, links with a greater amount of leakage flux than the branch 17. Consequently, the branch 16 will have greater reacta-nce than the branch 17 ,"the effect of thisbeing that the current through the winding element 13 di-v vides unequally, even though the ohmlc resistances of the several branches are equal,

the greater amount of current crowding 1 through the branch 17. Were this same condition present in each of the slots occupied by the portions or the windlng element 13 connected in serles, that s, if no PIOVlSlOIl were made for shifting the relative posi tionsof the several branches in the slots to in the winding would then be'considerably; greater han it each of the branches carried the same amount of current.

Considering the illustrative showing of Fig. 5, the conductors 16,, and 17,, may represent conductors of the same ohmic resistance nsulated one frorn another and carrycurrentbetween the termlnals t and 25 However, assume that, due to somereactive effect on the branch 16,, instead ofcurrents' of the same value flowing in the two branchea; the current flowing in branch 16,,

is considerably less than that flowing in the branch 17,. Now,-1n order to cause the cur rent to divide equally between the branches an artificial reactancemust be inserted in the branch 51, this reactance being designated R and being of such dimensions asto cause proportion between the several branches. 7

To illustrate the principle involved, con si'der that normally, with the parallel contne current. to divide in the proper nected branches of the same equivalent re- 7 sistance, say 1 ohm, each branch carries 5O amperes,

under which circumstances the total l? R- losses are-5O X 1: 2,500 wattsfor each branch, or a total of 5,000 watts; whereas, if, for some reason, thetotal current be caused to divide'unequally between the two branches, say 60 amperes in one.

branch and losses. ii:

1-0 in the other, the total 1 R v be ca i:3.eo0, plus 40 X 1,600,;ora total of 5200 watts: This particular unequal division or the total-currentithroughthe several branches gives an increased heat-loss of 200 watts. Like wise, this increase intotal I B loss would vary as the square of thedifference between currents in the two branches.

This principle is illustrated further in Fig. Gwherein the-conductiveelem nt. be-

tween the terminals t and t, is dividedv into three branches, 18, 19 and 21. It may present, the current in the several branches has a tendency to divideunequally, and that the branch 18 tends to carry the greatest part and the branch 21 the least. In order to cause the current to divide equally be tween the several branches artificial reactances R and R having. no effect on the ohmic resistances, are inserted in the branches 19 and 18, respectively, these reactances being of such value as to cause a proper division of the current between several branches and a reduction to a minimum of the heat losses in the conductive path between terminals t and t.

In general accordance with the principle outlined in the above explanation, assume that, when no. special provisions are made to prevent it,the current divides unequally between the branches 16 and 17 of the conductor 13, the branch 17 carrying the greatest part of the total current due to the greater reactance of the branch 16 on account or" theeflect of leakage flux in the'core. Of course, in the specific arrangement illustrated, wherein the section of a phase winding shown is made up of three coils 2 1, 25, 26,

one side of each coil being at the outer part of one of the slots 12,, 12 12 and the other side of each coil at the inner part of one of the slots 12,, 12 12,, as indicated in Figs. 1, 2, 3 and 4, the reactive effects due to leakage'fiux on the several branches of the conductive element of the winding may be balanced to some extent; nevertheless, there may be considerable difference in the current flowing in the two branches 16 17, and, hence, the general principleof this invention is applicable to this condition as well ,aslto the case where the branches are insulated throughout and so disposed in the slots of the core that the unbalancing efiec in the portions. located in the several slots is one of several is cumulative or where the result general unbalance between the branches.

The type of winding illustrated in Figs. 1, 2, 3 and 1 an ordinary one of the two layer type the section of he winding shown comprising the three coils 24, .25, 26, each being made up of a conductive element divided into two para lel branches insulated throughout the length of the coil and oined together at their end portions. The circuit through the several coils of the winding sections shown nn be traced from. the terminal T, where the Q: "is G1 the several branches 16, 17 are brought out and connected together by a conductive clip 28. Through out the entire length 0% the several coils the branches 16 17. are insulatedone from another. From the terminal T the coil 24 extends through the outer part of the slot 12,, makinga 180 degree bend at the Uturn at the rear end of the core and returning through the slot 12,, with the branch 16 at the bottom or inner end of the slot. The

ends of the several branches of each coil are spaced apart, as indicated generally in Figs. 1, 3 and 4-, to facilitate connection with the proper branches of other coils. The coils 25 and 26 are similarly arranged in the slots 12 12 and 12 12 respectively. The terminals of the branches 16 and 17 of the several coils are designated 16,, 16 16 16, and 17 17 17,, the subscript in each case denoting the slot from which the terminal emerges at the front side of the core, as indicated in Figs. 1 and 3. The terminals are brought out separately, with a terminal of one branch of one coil radially alined with a terminal of a like branch of an adjacent coil, so that the several branches may be readily connected in series throughout the several coils while maintaining the branches 16, 17 fully insulated throughout the entire length of the phase winding or section thereof.

The manner of connecting like branches of the several coils in series is fully disclosed in Figs. 1, 3 and at, wherein the terminal 17 of the coil 25 is racially alined with the terminal 17,, of the coil 24, the two being connected by conductor clip 29, the termi nal 16 of the coil 25 is brought out in radial alinement with the terminal 16,, of the coil 24 and is connected thereto by a conductive clip 31, the terminal 17 of the coil 26 is brought out in radial alinement with the terminal 17 of the coil 25 and is connected thereto by a conductive clip 32, and the terminal 16 of the coil 26 is brought out in radial alinement with the terminal 16 of the coil 25 and. is connected thereto by a conductive clip 34:. The terminals 16, and 17 of the branches 16 and 17 of the coil 26 are connected together by a clip 35 which is inturn connected to the terminal T,.

It will be noted that, if the winding is traced from one or" its terminals, as T to the other terminal, the superposed branches thereof are radially transposed as the winding progresses from each active zone to another. The, result is that the branch 16 has, in the instance disclosed, three conductors 16 16 16,, located at the very bottom of the respective slots and three conductors 16 16 16,, located at the very top of the respective slots, while the branch 17 has three conductors 17 f 17 17, and three conductors 17 17 17 located respectively in the third and second layers, counting from the air gap, in the respective slots. In general, then,

'b* reason of the better ma netic )ath around ncvertheless,even with this arrangement, it is the case quite often that the current does not divide equally between the several branches and, hence, there are present uncalled for heat losses. It is considered that the latter is the actual condition present in the case described and illustrated, it being assumed that the impedance of the branch erably in the form of a closed or partly closed ring of magnetic material, and being or such proportions as to render the total impedance of the branch 17 the same as that of the branch '16 in which leakage flux eXercises a greater reactive effect. Thisreactance 37 is preferably associated with a terminal portion of the branch 17, indicated in Fig. l as being associated with the terminal While, in the case illustrated, thetendency toward unbalanced currents in the several branches or strata of the conductive element of whichthe winding is constituted is counteracted to a considerable extent by reversal of the relative positions of the branches in the several slots, nevertheless, the general principle of this invention can ordinarily be utilized, even in this case, to a considerable advantage in improving the operating characteristics of the machine. Of course, the utility of theinvention is proportionately greater in cases where the design of the machine is such that the several parallel branches or strata are not so disposed throughout their full length that the V reactive effects of leakage flux are counteracted in a substantial part. Likewise, it will be apparent that, as to certain features of the invention, advantages are present independently of whether the parallel connected branches of the conductiveelement are maintained separate andinsulated one from an other throughout only single slot-occupying portions or throughout the entire winding or' a substantial portion thereof. Infact, advantages may be derived from the use of this invention in any case where there is a tendency for the current to divide unequally made for neutralizing in part the reactive effects due to leakage flux.

It should be understood that it is not desired that the invention as claimed be limited to the exact details of construction shown and described, forobvious modifications will occur to a person skilled in the art. It is claimed and desired-to secure'by LettersPatent:

1. In a dynamo electric machine a core provided with slots, an'inducedgwinding, raving end turns, comprising a plurality of comparatively heavy branches of substantially the same ohmic resistance and different inductive resistance radially superposed in the same slot, said branches being elec-- tric'ally connected together'only at the respective ends thereof, and means other than the relative disposition of the branches associated with end turns of said winding for equalizing the impedance of the several branches.

2. In a dynamo electric machine, a core provided with slots, an induced winding; having end turns, comprising a plurality of parallel connected comparatively heavy branches in the same slot, and artificial reactance-means associated with end turns of said winding and 'with the circuit of a branch or branches upon which leakage flux has less reactive effect than on another branch.

3. In adynamo. electric machine, a core provided with slots, an induced winding, having end turns, comprisingja plurality of parallel connected comparatively heavy branches in the same slot radially superposed therein, and artificial reactance-means associated with end turns of said winding I and with the circuit of a branch or branches prising a plurality of parallel connected comparatively heavy branches in the slots, andmeans, other than the relative disposition of the branches, associated with the end turns of said winding for insuring the current divides so as to secure uniform current density in the branches. l

5. In an alternating current dynamo elecric machine, a core provided with slots, an induced winding, having end turns, comprising a plurality of parallel connected comparatively heavy branches in the slots,

and means, other than-the relative disposi-' tion of the branches, associated with the end turns of said winding and with the branch disposed effectively nearest the air. gap of the machine for insuring the current divides so as to secure uniform current density in the branches.

6. In an alternating current dynamo-electric machine, a core, provided with slots, a winding comprising aplurality of parallel connected branches radially superposed and insulated one from another within said slots, and means inductively associated with an extending end portion of the branch that is subject to less reactive effects due to its position relative to the core, said means being eflective to cause the current to divide so as to insure uniform current density in the several branches.

7. In a dynam electric machine having a core, a winding including a plurality of form-wound coils disposed on said core, said winding comprising a plurality ofradially superposed branches electrically connected together only at the respective ends thereof, said coils having U-bend end-connectors whereby the induced portions of said branches are transposed radially as the winding progresses from one side of a coil to the other, and means for connecting the end of one coil to the beginning of the next coil so that as the winding progresses from one coil to the next the branches are radially transposed whereby the impedance of said branches is practically equalized.

8. In a dynamo-electric machine having a winding with a plurality of radially superposed branches connected at the respective ends thereof, means for practically equalizing the impedance of said branches including the radial transposition of said branches as the winding progresses from one active zone to another, and means for introducing an additional impedance in the branch having the lowest impedance for the purpose of substantially equalizing the impedance of the branches.

9. In a dynamo electric machine, the combination with a winding therefor having a plurality, of parallel connected branches, of means associated with a branch having a lower reactance than another branch for introducing an additional reactance in said branch without altering the ohmic resistance of said branch.

10. In a dynamo electric machine, the combination with a winding therefor having a plurality of parallel connected branches of a ring-like member of magnetic material associated with a branch having a lower reactance than another branch, whereby an additional reactance is introduced in said branch without altering the ohmic resistance of said branch.

In testimony whereof, the signature of the inventor is afiixed hereto.

ROBERT E. WILLIAMSON. 

